This article provides details on how to resume email service for Outlook 2011/16 email clients on MacOS app after your email account has been migrated to Microsoft Servers.
Once your email account has been migrated to the Microsoft servers you will receive a prompt stating that Outlook was redirected to get new server settings. Tick 'Always use my response for this server' and click Allow.
Outlook 2016 Outlook 2011
Close the Outlook application an re-open it. If prompted enter your password.
Normal email service will now resume.